Tokkai Hei No. 9-303173 published by the Japan Patent Office in 1998 relating to fuel injection control of an internal combustion engine, discloses a method of calculating a fuel injection amount using a wall flow model.
Wall flow means flow of fuel formed when some of the fuel injected from the fuel injector adheres to the wall surface of a combustion chamber or an intake port as well as to the valve body of an intake valve. Some of the wall flow vaporizes and burns, and some vaporizes after combustion is complete and is discharged from an exhaust valve without being burnt. The remaining part of the wall flow remains in the combustion chamber until the following combustion cycle.
The ratio of injected fuel which forms a wall flow is called the adhesion ratio. Of the fuel forming the wall flow, the ratio of fuel remaining in the combustion chamber in the wall flow state without vaporizing is referred to as the residual ratio.
In the prior art, a fuel behavior model of injected fuel is constructed having adhesion ratio and residual ratio as parameters, and by varying the parameters according to intake air pressure, it is attempted to comprehend the behavior of the fuel supplied to the internal combustion engine, and to improve the precision of fuel supply control.